1. Field of the Invention
The present invention relates to a layout method for electronic components of a circuit board, and more particularly to a layout method for electronic components of a double-sided surface mount circuit board.
2. Related Art
A printed circuit board (PCB), serving as an electrical carrier board, is capable of gathering a plurality of electronic components to form a circuit system having integral functions, so that the PCB is an indispensable basic component for all types of electronic products.
In order to miniaturize the electronic products and enhance the reliability thereof, recently, the electronic components are combined to the circuit board through a surface mount technology (SMT) instead of a conventional combination manner of perforation and insertion. The electronic components can be quickly mounted on the PCB through the SMT, thereby achieving the advantages of high functional density, light weight, low inductance-capacitance and impedance, lower production cost, and the like. Therefore, the SMT is widely applied to electronic telecommunications, high frequency circuits, communication systems, aeronautics, household appliances, mechanics, and other fields.
In order to further simplify the layout design on the PCB and improve the unit density of the PCB, a double-sided SMT of the PCB is developed.
A conventional double-sided surface mount process of the PCB mainly has the following steps. A paste is first printed on a pre-determined position of a circuit board. Then, a surface mount device (SMD) is placed on the printed paste. A reflow soldering process is performed on the circuit board disposed with the SMD, so that the paste on the circuit board is melted, and wires on the SMD are soldered on the circuit board, thereby completing the fabrication process on one side of the circuit board. Afterward, the circuit board is turned over to have the other side without the SMD facing upwards, and the same surface mount process is repeated to complete the double-sided surface mount process of the PCB.
Although the conventional double-sided surface mount process can successfully fix the SMDs on the two side surfaces of the PCB respectively, the process is inapplicable to specific electronic components, for example, electronic devices in the form of a plated through hole (PTH).
Particularly, if a PTH device is formed in advance on one side of the PCB, when the other side of the PCB is handled in the double-sided surface mount process, the height of the soldered PTH device is different from that of the SMD, which may result in a tin pick-up problem when the PTH device passes through a wave solder tin oven.
Therefore, the PTH device needs to be additionally soldered manually, such that the conventional double-sided surface mount process of the PCB becomes rather complicated, which may give rise to limitations like the processing time cannot be effectively shortened, the manufacturing cost cannot be lowered, and the product quality cannot be stably maintained.